The present invention relates to a spindle motor control system for a magnetic disk apparatus and, more particularly, to a spindle motor control system for controlling a plurality of disk apparatuses to be driven in synchronism with each other.
In a conventional spindle motor control system for a magnetic disk apparatus, speed control is performed for each spindle motor within the range of upper and lower limits of the rotation speed of the spindle motor, and then synchronization between the respective spindle motors is controlled. The rotation speeds of the plurality of spindle motors differ from each other and variations in rotation speed also differ from each other because loads acting on the motors are different. Therefore, it is difficult to maintain the rotation speeds and the phases of the plurality of spindle motors coincident with each other for a long period of time.
The present inventor has invented a multi-spindle synchronization control system which eliminates the above drawback of the conventional technique and can easily and accurately synchronize a plurality of magnetic disk units and filed a patent application for the system on June 17, 1988 (U.S. patent application Ser. No. 207,984).